Reference Guide For Pharmaceutical Calculations
Krisman
REFERENCE GUIDE FOR
PHARMACEUTICAL
CALCULATIONS
2014-2015 EDITION
MANAN SHROFF
www.pharmacyexam.com
1
Reference Guide For Pharmaceutical Calculations
Krisman
This reference guide is not intended as a substitute for the advice of a physician. Students or
readers must consult their physician about any existing problem. Do not use any information of this
reference guide for any kind of self treatment. Do not administer any dose of mentioned drugs in
this reference guide without consulting your physician. This is only a review guide for preparation
of pharmaceutical calculations.
The author of this reference guide is not responsible for any kind of misinterpreted, incorrect or
misleading information or any typographical errors in this guide. Any doubtful or questionable
answers should be checked in other available reference sources.
All rights reserved.
No part of this guide may be reproduced or transmitted in any form or by any means, electronically
photocopying, recording or otherwise, without prior written permission of the publisher.
RXEXAM is a registered trademark of Pharmacy Exam of Krishna Publication inc. Any
unauthorized use of this trade mark will be considered a violation of law.
NAPLEX, PARE and FPGEE exams are federally registered trademark owned by National
Association Board of Pharmacy (NABP). PTCB is registered trade mark owned by Pharmacy
Technician Certification Board and this review guide is in no way authorized or sponsored by
NABP or PTCB.
www.pharmacyexam.com
2
Reference Guide For Pharmaceutical Calculations
Krisman
PREFACE
I am very pleased to announce to release of the 2014-2015 Edition for The Reference
Guide For Pharmaceutical Calculations. It is a resourceful practice guide for preparation of the
NAPLEX, FPGEE, PTCB and California Pharmacy Board exams.
This edition contains 650 calculation problems to prepare students for an actual exam. In
this Third Edition, I have also included some calculations on creatinine clearance and opioid
conversions.
The NAPLEX, FPGEE, PTCB and California Pharmacy Board exams are currently
putting more emphasis on calculation problems. A significant percentage of these exams, at least
25% to 30%, consist of calculations.
Calculations related to I.V., I.V. infusion, TPN and dosages are very important in retail and
institutional pharmacy settings. This guide will provide complete practice on related calculation
problems and help in the achievement of an exceptional score on the examinations.
Best of luck,
Manan Shroff
www.pharmacyexam.com
3
Reference Guide For Pharmaceutical Calculations
Krisman
TABLE OF CONTENTS
SECTION - I
1.
CALCULATIONS
9
2.
ANSWERS
45
SECTION - II
1.
PRACTICE CALCULATIONS
87
2.
ANSWERS
129
www.pharmacyexam.com
4
Reference Guide For Pharmaceutical Calculations
Krisman
COMMONLY USED UNITS FOR PHARMACEUTICAL CALCULATIONS
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
1 kilogram
1 gram
1 milligram
1 microgram
1 microgram
1 nanogram
1 grain
1 liter
1 ounce (oz)
16 ounce (oz)
1 pint
1 quart
1 gallon
1 kg
1 lb
1 teaspoonful
1 tablespoonful
1 teacupful
Density
Proof gallon
% strength
Proof gal
PV
PV
Equivalent wt
mEq
mOsmol/L
pH
Young (child)
Clark’s
Child’s dose
Fried’s rule
FP of blood
*
*
*
*
*
*
*
*
*
Each gm of hydrous dextrose provides
Each gm of anhydrous dextrose provides
Each gm of fat provides
Each gm of protein/aminoacid provides
Each gm of medium chain triglyceride (mct)
Each gm of glycerol provides
Each cc of alcohol provides
1 cc of 10% fat emulsion provides
1 cc of 20% fat emulsion provides
www.pharmacyexam.com
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
1000 grams
1000 milligrams
1000 micrograms
0.001 milligrams
10-6 grams
10-9 grams
65 milligrams
1000 cc
30 cc
480 cc
=
1 pint
480 cc
960 cc
=
2 pints
3840 cc
=
8 pints
=
4 quarts
2.2 lbs
454 grams
5 cc
15 cc
120 cc
weight/volume
(gal x % v/v strength) / 50% v/v
proof spirit / 2
(gal x proof spirit) / 100
nRT
W/M x R x T
molecular weight / number of valence
equivalent weight in mg / 1000
(weight of substance [g/L] x no of species x 1000) / mol wt
pKa + log (salt/acid)
(age in years / age + 12) x adult dose
(weight in lbs / 150) x adult dose
(body surface area of child / 173 mm2 ) x adult dose
(age in months / 150) x adult dose
-0.52oC
=
=
=
=
=
=
=
=
=
3.4 calories / kcal
4 calories / kcal
9 calories / kcal
4 calories / kcal
8.3 calories / kcal
4.3 calories / kcal
5.6 calories / kcal
1.1 calories / kcal
2.0 calories / kcal
5
Reference Guide For Pharmaceutical Calculations
Krisman
*
*
pH
pH
=
=
pKa + log (salt/acid) or (ionized/unionized) (for weak acid)
pKw - pKb + log (base/salt)
(for weak base)
*
B
=
2.3 x C Ka x H3O+
(Ka + H3O+)2
(Van slyke’s buffer capacity equation)
where, C = total buffer concentration, H3O+ = hydrogen ion concentration
*
Bmax
=
0.576 x C
(maximum buffer capacity)
where C = total buffer concentration
980 cm/sec2
0.082 lit atm / mole deg
4.184 x 107 erg
6.0221 x 1023 mole-
*
*
*
*
Acceleration gravity (g)
Gas constant (R)
1 calorie
Avogrado’s number
=
=
=
=
*
K = 2.303 log Co
t
C
where Co = initial concentration of drug
where C = concentration of drug at time ‘t’
*
t 1/2 = 0.693/K
where t1/2 = half life of drug
where K = rate constant
*
Vd = M/Cp
where Vd = volume of distribution
where M = amount of drug in body
where Cp = plasma concentration of drug
*
Ri = Css x Vd x K
where Ri = rate of infusion
where Css = steady state plasma concentration
where Vd = volume of distribution
where K = drug elimination constant
*
Ld = Css x Vd
where Ld = loading dose of drug
where Css = steady state plasma concentration
where Vd = volume of distribution
*
Normality (N):
It is defined as the presence of number of gram equivalent
weight of solute in 1000 ml or (1L) solution.
*
Molarity (M):
It is defined as the presence of number of moles of solute in
1000 ml or (1L) of solution.
*
Molality (m):
It is defined as the presence of number of moles of solute in
1000 gm of solvent.
www.pharmacyexam.com
6
Reference Guide For Pharmaceutical Calculations
9 (oC) = 5 (oF) - 160
*
Temperature conversion:
*
CrCl
*
CrCl (female) =0.85 x male (CrCl)
*
The number of vials of Digibind required =
=
Krisman
weight (kg) x (140-age)
72 x serum creatinine (mg/dL)
www.pharmacyexam.com
Total digitalis body load in mg x 0.8
0.5mg of digitalis bound
7
Reference Guide For Pharmaceutical Calculations
Krisman
QUESTIONS
www.pharmacyexam.com
8
Reference Guide For Pharmaceutical Calculations
1.
Sulfur
3%
Salicylic acid
3%
White Petrolatum.............q.s. 80 gm
Find out the amount of Sulfur required to fill the
above prescription?
a.
b.
c.
d.
1.2 gm
2.4 gm
3.0 gm
4.8 gm
2.
How many grams of Dextrose are required to prepare 5% of 500 cc solution?
a.
b.
c.
d.
2.5 gm
25 gm
55 gm
5 gm
3.
How much Lidocaine is required to prepare 1 : 1000, 30 cc of solution of Lidocaine?
a.
b.
c.
d.
10 mg
0.03 mg
30 mg
300 mg
Krisman
6.
How many cc of 75% alcohol should be
mixed with 10% of 1000 cc alcohol to prepare
30% of 500 cc alcohol solution ?
a.
b.
c.
d.
346.16 cc
234.43 cc
153.84 cc
121.12 cc
7.
How many grams of Heparin are required
to prepare 1 quart of 0.45% solution?
a.
b.
c.
d.
2.16 gm
4.32 gm
0.45 gm
4.5 gm
8.
If a prescription reads “Augmentin 875
mg po bid x 10 days,” how many cc of Augmentin 250 mg/5 cc are required to fill a
ten-day supply?
a.
b.
c.
d.
350 cc
35 cc
17.5 cc
5 cc
9.
How many milligrams are equal to
1/150 gr of Nitroglycerine?
If 250 mg of Cefazolin powder are diluted with water up to the 250 cc mark, what is
the % of drug in the final solution ?
a.
b.
c.
d.
a.
b.
c.
d.
4.
150 mg
65 mg
55 mg
0.43 mg
5.
How much Atropine is required to dispense 1 quart of 1 in 100 solution?
a.
b.
c.
d.
9.6 mg
1.48 gm
2.3 mg
9600 mg
www.pharmacyexam.com
10%
0.1%
11%
0.01%
10.
If 1 teaspoonful of Thioridazine concentrated solution (30 mg/cc) is diluted up to the 480
cc mark with plain water, what is the strength of
drug in mg/ml in the final
solution ?
a.
b.
1mg/cc
0.52 mg/cc
9
Reference Guide For Pharmaceutical Calculations
c.
d.
0.31 mg/cc
0.75 mg/cc
11.
If a prescription reads “Diphenhydramine
50 mg po hs x 30 days ”, what would be the
dispensed quantity of drug in ml (12.5 mg / 5 cc)
for thirty-day supply?
a.
b.
c.
d.
20 cc
5 cc
300 cc
600 cc
Krisman
a.
b.
c.
d.
4
3
1
2
16.
If 1000 tablets of Risperdal 1 mg cost
$2250 and the mark-up on prescription is 20%,
what would be the retail price for 30 tablets?
a.
b.
c.
d.
$150
$17
$500
$81
12.
Erythromycin 2% 60 cc topical solution
contains:
a.
b.
c.
d.
2 gm erythromycin
2.4 gm erythromycin
0.6 gm erythromycin
1.2 gm erythromycin
17.
How much Clobetasole is present in 60
gm of 0.5% ointment?
a.
b.
c.
d.
1.2 gm
3.0 gm
2.1 gm
0.3 gm
13.
If 60 mg of elementary iron are present in
325 mg of ferrous sulfate, what is the % of
elementary iron?
a.
b.
c.
d.
20.00%
10.25%
18.46%
9.25%
18.
If the ratio of ionized to unionized species of drugs is 103 and PKa = 2.2, what is the
pH of the solution?
a.
b.
c.
d.
2.2
0.8
5.2
3.0
14.
If 60 gm of 1% hydrocortisone are mixed
with 80 gm of 2.5% hydrocortisone, what is the
% of hydrocortisone in the final mixture?
a.
b.
c.
d.
2.2% w/w
1.85% w/w
0.25% w/w
1.75% w/w
15.
If a prescription reads “100 mcg cyanocobalamin i.m. every week”, how many ampuls
of 1000 mcg / cc are required to fill a month
supply?
www.pharmacyexam.com
19.
If a prescription reads “Augmentin 875
mg by mouth twice a day”, how many cc of
Augmentin 400 mg/5 cc are required to dispense
a 10 day supply?
a.
b.
c.
d.
10.93 cc
218.75 cc
75.00 cc
100.00 cc
20.
Find out the weight in gm of 500 cc glycerine. [Specific gravity = 1.25 gm/ml]
10
Reference Guide For Pharmaceutical Calculations
a.
b.
c.
d.
625 gm
50 gm
400 gm
0.25 gm
Krisman
26.
How many 500 mg tablets of erythromycin are required to prepare 240 cc of 2% solution of erythromycin?
Find out the volume of 5 lb of glycerine.
[density = 1.25 gm/ml]
a.
b.
c.
d.
3
5
6
10
a.
b.
c.
d.
27.
How many milligrams are equal to 1/150
21.
1816 cc
6.25 cc
637 cc
40 cc
grains?
Calculate the weight of 500 cc of acid.
[density of acid = 2.5 gm/ml]
a.
b.
c.
d.
a.
b.
c.
d.
28.
22.
1000 gm
1250 gm
500 gm
200 gm
How many 975 mg tablets of aspirin are
required to prepare 100 tablets of 1 grain?
Find out the ratio of ionized to unionized
species of drugs at pH = 7. [pKa = 5]
a.
b.
c.
d.
a.
b.
c.
d.
29.
23.
10
1
100
1000
0.65 mg
1.21 mg
0.43 mg
1.56 mg
6 tablets
10 tablets
5 tablets
3 tablets
If 3 capsules of 150 mg of Clindamycin
are added to 150 cc of 1% Cleocin topical solution, what is the % of Clindamycin in the final
mixture ?
24.
If the pH of the solution is 3, what is the
concentration of H3O+ in gm ion /L?
a.
b.
c.
d.
0.01 gm-ion/L
1 x 103 gm-ion/L
0.05 gm-ion/L
10-3 gm-ion/L
25.
What is the pH of a solution having a ratio
of ionized to unionized species of drugs of
1 x 10-6 ?[PKa = 7]
a.
b.
c.
d.
2
5
3
1
www.pharmacyexam.com
a.
b.
c.
d.
1.5%
1.3%
1.1%
0.9%
30.
The adult dose of a drug is 500 mg. What
is the dose for a 2 year old child? [use young
rule]
a.
b.
c.
d.
71.42 mg
101.53 mg
25.46 mg
31.18 mg
11
Reference Guide For Pharmaceutical Calculations
280. How many mls of Infed (50mg/2 ml) are
required for a patient with blood loss of 350mls?
[Patient’s hematocrit = 25%]
a.
b.
c.
d.
1.75
2.52
3.46
4.15
281. If 1 teaspoonful of Diazepam concentrated solution (5mg/cc) is diluted up to the 1 pint
mark with plain water, what is the strength of drug
in mcg/ml in the final solution?
Krisman
a.
b.
c.
d.
1.21
1.85
2.14
3.47
285. How many mEqs of K+ are present in
750mg of a KCl capsule? [ K+ = 39, Cl- = 35.5]
a.
b.
c.
d.
10
19
63
54
286. How many grams of CaCl2 are required
a.
b.
c.
d.
12
52
22
35
282. If a normal dose of a drug is 0.02mg/kg/
day, how many 250mcg/50cc ready-infusion bags
are required to fill the above order ? [Patient’s
weight = 155 lbs.]
to prepare a 1 gallon solution that contains 20
meq of calcium ions? [mw CaCl2 = 111gm/mole]
a.
b.
c.
d.
2.52
1.11
3.25
4.54
287. What is the half-life of a drug that has a
rate of constant of 0.025 minutes-?
a.
b.
c.
d.
3
6
5
4
a.
b.
c.
d.
0.22 hrs
0.56 hrs
0.65 hrs
0.46 hrs
283. If 10cc of Lidocaine 0.05mg/cc are
diluted with water up to the 50cc mark, what
would be the strength of drug in mcg/ml?
a.
b.
c.
d.
10
60
90
40
284. Four grams of Levofloxacin (mixed with
500cc 0.9% NaCl) is administered via slow I.V.
infusion over 24 hours. If the I.V. set delivers 10
drops/ml, what would be the rate of flow in drops/
min?
www.pharmacyexam.com
287. If the I.V. dose of a drug is 10mg/I.V./kg,
what would be the plasma concentration of the
drug in micrograms per ml for a patient weighing
95 lbs.? [An apparent volume of distribution of
drug is 0.025 L/kg]
a.
b.
c.
d.
400
254
333
652
41
Reference Guide For Pharmaceutical Calculations
Krisman
288. If a prescription calls to dispense 8 fl oz
292. If a prescription reads 2 capsule (500mg
of KCl in such a way that 1 teaspoonful of solution contains 0.5 mEqs of drug, how many grams
of KCl are required to prepare the above prescription? [mw of KCl = 74.5gm/mole]
Dicloxacillin) daily for 7 days, how many teaspoonfuls of 500mg/5cc oral suspension are
required to fill the complete order?
a.
b.
c.
d.
2.65
1.78
6.52
9.11
a.
b.
c.
d.
42
11
14
32
293. If the serum creatinin concentration of a
289. One teaspoonful of Risperdal concentrated solution (5mg/5cc) is diluted up to 500cc
with distilled water; 5cc of this resultant solution
are diluted up to 250cc with distilled water. What
would be the concentration of drug in mcg/cc in
the final solution?
a.
b.
c.
d.
1.2
0.2
0.625
0.0002
65-year-old male patient is 3.5mg/dl, what is
creatinine clearance in ml/minute? [Patient’s weight
= 160 lbs.]
a.
b.
c.
d.
76
34
59
22
294. How many milligrams of Erythromycin are
required to prepare a one pound 0.03% ointment?
290. 10cc of 0.25% KCl solution, 20cc of
3.25% NaHCO3 solution and 20cc of 2.25%
CaCl2 are mixed with a 5% 500cc dextrose solution. The infusion should be administered over
8 hours. What is the flow rate in drops/min? [I.V.
set delivers = 10 drops/cc]
a.
b.
c.
d.
136
232
143
114
295. A prescription says to take 10mg of
a.
b.
c.
d.
5
20
12
17
291. If the serum creatinine value for Jennifer
is 1.5mg/dl, what would be the creatinine
clearance value in ml/min? [Patient’s age = 45
years; Weight = 180lbs.]
a.
b.
c.
d.
65ml/min
80ml/min
23ml/min
61ml/min
www.pharmacyexam.com
Morphine po q4h. Below is a chart with the
recommended initial Duragesic dose based upon
daily oral Morphine dose:
Oral-24 hour Morphine
(mg/day)
45-134
135-224
225-314
315-404
Duragesic dose
(mcg/h)
25
50
75
100
How many 25mcg/hr Duragesic patches are
required to fill a 10-day supply?
42
Reference Guide For Pharmaceutical Calculations
a.
b.
c.
d.
5
9
3
10
298. If a prescription says “Augmentin 250mg
po tid x 7 days,” how many cc of Augmentin
250mg/5 cc are required to fill a 7-day supply?
296. A 45-year-old patient is taking 25mg of
Meperidine by mouth, six times day, to relieve
pain associated with knee injury. If a prescriber
wants to switch him over to Hydromorphone, how
many mls of 0.5mg/ml Hydromorphone suspension are required to fill a 30-day supply?
Oral Prior
(opioid)
(multiplication factor)
Parenteral Prior
(opioid)
Oxycodone
0.25
Codeine
0.04
Morphine
0.12
Meperidine
0.02
Hydromorphone 1.0
a.
b.
c.
d.
Krisman
N/A
N/A
N/A
N/A
N/A
90
180
150
240
297. A prescription says a 25mcg/hr patch of
a.
b.
c.
d.
125
211
105
90
299. If a normal dose of a drug is 0.05mg/kg/
day, how many 500mcg/50cc ready-infusion bags
are required to fill the above order? [Patient’s
weight is 110lbs.]
a.
b.
c.
d.
4
3
5
6
300. How many milliosmols per 100ml are
present in 25ml D25W solution? [mw of dextrose
= 180gm/mole]
a.
b.
c.
d.
111
451
139
214
Duragesic TDS is to be changed every 72 hours.
If a prescriber wants to switch this to Oxycodone,
how many 5mg tablets of Oxycodone are required
to fill a 7-day supply? [Assume 18 hrs after removal of the transdermal fentanyl patch,
approximately 10mg of oxycodone q12h can be
substituted for each 25mcg/h of transdermal
fentanyl to start.]
a.
b.
c.
d.
140
12
52
28
www.pharmacyexam.com
43
Reference Guide For Pharmaceutical Calculations
Krisman
ANSWERS
www.pharmacyexam.com
44
Reference Guide For Pharmaceutical Calculations
Krisman
1. (b) 2.4 grams.
To prepare 65 (30%) 20 parts (75%) needed
To prepare 500 (30%) ?
The amount of sulfur required to fill the
above prescription is 80 x 3 = 2.4 grams.
100
=
500 x 20 = 153.84 cc (75%) alcohol
65
500 x 5 = 25 grams of dextrose.
100
If we mixed 153.84 cc of 75% alcohol with
346.16 cc [500 cc - 153.84 cc] of 10% alcohol,
then we can get 500 cc of 30% alcohol solution.
3. (c) 1: 1000 is generally interpreted as 1 gm
7. (b) We want to prepare 1 quart (960 cc) of
in 1000 cc of solution. The amount of lidocaine in
30 cc of 1:1000 solution can be calculated as
follows:
=
2. (b) 500 cc of 5% Dextrose solution contains:
0.45% heparin solution, therefore we can say
960 x 0.45
100
=
4.32 gm.
= 30 x 1 = 0.03 gm = 30 milligrams.
1000
4.32 gms of heparin are required.
4. (d) 1 grain is equal to 65 milligrams, there-
8. (a) This type of calculation is classified as a
fore 1/150 grains are equal to:
= 1 x 65 = 0.43 milligrams
150
5. (d) 1 in 100 solution is interpreted as 1 gm of
drug in 100 cc of solution. We want to find out
how much atropine is required to dispense 1 quart
(960 cc) of 1 in 100 solution, therefore:
= 960 x 1 = 9.6 gm atropine = 9600 mg.
100
6. (c) To solve this type of problem, we need
to use the alligation method.
dosage calculation and can be calculated as follows:
We have a suspension of Augmentin 250 mg/5 cc
and we want to dispense dose of 875 mg,
= 5 x 875 = 17.5 cc
250
The patient is taking 875 mg twice a day and
therefore:
= 2 x 17.5 cc = 35 cc per day.
Patient is taking drug for 10 days therefore,
= 35 x 10 = 350 cc would be the dispensed quantity of drug.
9. (b) 250 mg (0.25 gm) of cefazolin powder
are diluted with water up to 250 cc mark and we
want to find out the % of drug in the final solution.
=
100 x 0.25 = 0.1%
250
www.pharmacyexam.com
45
Reference Guide For Pharmaceutical Calculations
10. (c)
Krisman
1 teaspoonful (5 cc) of Thioridazine solution (30mg/cc) contains 150 mg of
drug. This solution is diluted up to a mark of 480
cc therefore:
15. (c)
=
= 100 = 0.1 cc of drug every week.
1000
150 = 0.31 mg/ml
480
11. (d)
We have 12.5mg/5cc Benadryl
solution. We want to dispense a 50 mg dose:
1 ampul
Patient is taking 100 mcg of the drug I.M. every
week, therefore:
The number of cc required for a 1 month supply:
= 0.1 x 4 = 0.4 cc
=
50 x 5 = 20 cc for 1 day
12.5
For 30 day supply:
The correct answer should be 1 ampul.
16. (d)
=
20 x 30 = 600 cc.
12. (d)
Erythromycin 2% topical solution
contains = 60 x 2
100
1000 tablets of Risperdal 1mg
cost $2250. The % mark up on prescriptions is
20%.
Therefore the retail price of 1000 tablets would
be:
= 1.2 gm of erythromycin.
= 120 x 2250 = $2700
100
13. (c)
** Each $100 cost = $120 retail cost**
The % of elementary iron can be
found as follows:
= 100 x 60 = 18.46%
325
14. (b)
The amount of Hydrocortisone in
60 gm, 1%:
60
100
= 0.6 gm of hydrocortisone.
Amount of hydrocortisone in 80 gm, 2.5%
80 x 2.5 = 2 gm hydrocortisone
100
% of hydrocortisone in final mixture
= 100 x 2.6 (2 gm + 0.6 gm)
140 (80 gm + 60 gm)
Price for 30 tablets would be:
= 30 x 2700 = $81
1000
17. (d)
We want to find out the quantity
of Clobetasole present in 60 grams of 0.5% ointment.
= 60 x 0.5 = 0.3 gm of clobetasole.
100
18. (c)
A pH of the solution can be found
by the following formula:
pH
= pKa + log ionize
unionize
= 1.85% w/w.
www.pharmacyexam.com
46
Reference Guide For Pharmaceutical Calculations
= 2.2 + log 103
= 2.2 + 3
= 5.2
19. (b)
We have 400 mg/5 cc Augmentin in stock. We want to find the dispensed quantity for a 10-day supply.
Krisman
24. (d)
3 = - log [H3O+]
-3 =
log [H3O+]
[H3O+] = 10-3 gm ion/L
25. (d)
= 875 x 5 = 10.93 cc for each dose
400
The patient is taking a dose twice a day for 10
days therefore :
= 10.93 x 2 x 10
= 218.75cc
pH = - log [H3O+]
pH = pKa + log [salt/acid]
pH = 7 + log[ 10-6]
= 7-6
= 1
26. (d)
240 cc 2% Erythromycin solu-
tion contains:
20. (a) Weight in grams = no of ml x sp gr
= 240 x 2 = 4.8 gm of Erythromycin
100
= 500 cc x 1.25 gm/cc
= 625 gm
The number of 500 mg tablets of Erythromycin:
21. (a)
Weight = density x volume
= 4800 = 9.6 10 tablets.
500
Volume = weight
density
27. (c)
=
5 x 454(1 lb = 454 gm)
1.25
= 1 x 65 = 0.43 mg
150
=
1816 cc glycerine.
28. (a)
22. (b)
1 grain is equal to 65 mg
therefore:1/150 grains will contain:
100 tablets of 1grain of Aspirin
contains: 100 x 65 = 6500 mg of Aspirin.
Weight = density x volume
The number of 975 mg tablets of Aspirin:
= 2.5 x 500
= 1250 gm of acid.
= 6500 = 6.66  6 tablets
975
23. (c)
pH = pKa + log salt
acid
7 = 5 + log salt
acid
log [salt/acid] = 2
29. (b)
1 % 150 cc Cleocin solution
contains:
= 150 x 1 = 1.5 gm Clindamycin
100
salt/acid = 102 , ratio of ionized to unionize drug
will be 100.
www.pharmacyexam.com
47
Reference Guide For Pharmaceutical Calculations
Krisman
The addition of 3 capsules each weighing 150 mg
will result in: 1.5 gm + 0.45 gm = 1.95 gm
= Body surface area of child x adult dose
173 mm2
% of Clindamycin in final mixture would be:
= 20 x 100
173
= 1.95 x 100 = 1.3%
150
= 11.56 mg
30. (a)
34. (d)
71.42 mg
Young rule = age in year x adult dose
age + 12
= 2 x 500 = 71.42 mg
14
31. (a)
1 grain is equal to 65 mg, therefore 10 grains contain
= 10 x 65 = 650 mg of the drug.
35. (c)
Patient weight is 156 lbs, therefore weight in Kg would be 156 = 70.9 kg.
2.2
100 mg
Clark’s rule = Weight in lbs x adult dose
150
A normal therapeutically recommended dose of
drug is 10mg/kg/day, therefore the dose in the
above patient is:
= 20 x 750 = 100 mg
150
= 10 x 70.9
= 709 mg
32. (c)
According to Fried’s rule:
Each ready-infusion-bag contains 250 mg of drug,
so the number of bags required to fill the order
would be
= age in months x adult dose
150
= 709 = 2.83  3 bags.
250
= 15 x 325 = 32.5 mg
150
The dropper is calibrated to deliver 325 mg of
Iron sulfate in 0.6 cc, therefore:
36. (b)
0.06 cc
= 0.6 x 32.5 = 0.06cc
325
33. (d)
11.56 mg
A child dose can be calculated by:
www.pharmacyexam.com
1/100 grains contains:
= 1 x 65 x 1000
100
= 650 micrograms
[1 mg = 1000 mcg]
A prescription calls for 50 mcg of a drug three
times a day for 10 days, therefore the number of
tablets required to fill the order is:
= 50 x 3 x 10 = 2.30  3 tablets
650
48
Reference Guide For Pharmaceutical Calculations
Krisman
37. (a)
41. (d)
= 30 x 125 = 3750 mcg of Lanoxin.
An adult dose of drug can be calculated by the
following formula:
A patient is taking 125 mcg of
Lanoxin every day, therefore to fill a 30 day order,
Each ml of Lanoxin elixir provides 50 mcg of a
drug, therefore the number of cc required to fill
the entire order is:
= 3750 = 75 cc of Lanoxin elixir.
50
Body surface area x adult dose
173 mm2
= 110 x 750 = 476.87 mg  477 mg
173
42. (d)
38. (a)
477 mg
A prescription reads to dissolve
2 gm of Guaifenesin in 100 cc of plain water,
therefore the amount of drug present in 1 teaspoonful (5 cc) of solution would be
contain:
= 5 x 2000 = 100 mg = 100 = 1.53 grain
100
65
43. (c)
240cc of 10% solution will
= 240 x 10 = 24 gm of drug.
100
6.75 gm sodium chloride
The amount of sodium chloride required:
39. (b)
100 mg of Lactaid is equal to 4500 units, therefore 1 unit is equal to:
= 750 x 0.9 = 6.75 gm of sodium chloride
100
44. (b)
= 100 = 0.02 mg of Lactaid
4500
D25W will be interpreted as 25%
Dextrose solution.
The amount of dextrose present:
40. (c)
28 cc
A 7 year-old child is taking 50 mg Ampicillin by
mouth twice a day for 7 days, therefore:
= 500 x 25 = 125 gm of dextrose.
100
45. (a)
= 50 x 2 x 7
= 700 mg of Ampicillin
1 : 1000 solution is interpreted
as 1 gm of drug in 1000 cc of solution.
The amount of Lidocaine required:
We have 125 mg/5 cc suspension in stock:
= 5 x 700 = 28 cc
125
www.pharmacyexam.com
= 30 x 1 = 0.03 gm = 30 mg of Lidocaine
1000
49
PRACTICE TEST
1.
How many milligrams are present in a
1/150 gr Nitrostat tablet?
a.
b.
c.
d.
1.2 mg
0.43 mg
45 mg
3.5 mg
2.
How many 1/200 gr of tablets can be
prepared from 500 mg of active ingredient?
a.
b.
c.
d.
167
432
1538
1100
3.
How many milligrams of Guiafenesin will
be present in 480cc (15 mg/5 cc) of solution?
a.
b.
c.
d.
908 mg
1440 mg
1000 mg
521 mg
4.
If the retail cost of each Zyprexa tablet is
$2.40, what would be the retail cost for 30 tablets?
a.
b.
c.
d.
72
111
24
67
5.
How many grams of dextrose are required
to prepare a 1000 cc D5w solution?
a.
b.
c.
d.
125 gm
75 gm
50 gm
500 gm
6.
How much atropine is required to prepare a 1:500, 500 cc solution of atropine ?
www.pharmacyexam.com
a.
b.
c.
d.
0.5 gm
0.005 gm
10 gm
1 gm
7.
How many grams of Lidocaine are required to dispense 1 quart of 1 in 50 solution?
a.
b.
c.
d.
11.4 gm
5 gm
19.2 gm
21 gm
8.
How many calories are provided by 1
quart of a 1 in 500 solution of dextrose?
a.
b.
c.
d.
11.2 calories
9.55 calories
55.6 calories
6.53 calories
9.
How much Xylocaine is required to prepare 30 cc of a 1:500 solution of Xylocaine?
a.
b.
c.
d.
120 mg
90 mg
60 mg
30 mg
10.
In what proportion should 49% alcohol
be mixed with water to prepare 1000 cc of a
25% alcohol solution?
a.
b.
c.
d.
30.5 cc
810 cc
111 cc
510.2 cc
11.
How much Heparin is required to dispense a 0.25% 750 cc solution?
a.
b.
c.
d.
1.875 gm
5.25 gm
0.115 gm
2.10 gm
87
Reference Guide For Pharmaceutical Calculations
12.
If a prescription calls for “Biaxin 500 mg
po bid x 10 days”, how many cc of Biaxin 125
mg/5 cc are required to dispense a 10 day supply?
a.
b.
c.
d.
200 cc
100 cc
400 cc
50 cc
13.
If a prescription is written to take 50 mg
of diphenhydramine by mouth four times a day
for 5 days, how many cc of 12.5 mg/5 cc diphenhydramine solution are required to dispense 5 day
supply?
a.
b.
c.
d.
400 cc
20 cc
80 cc
10 cc
14.
If 125 mcg of a drug are diluted with water up to 50 cc, what is the % of drug ?
a.
b.
c.
d.
0.25%
1.25%
0.00025%
0.0025%
15.
If 1 tablespoonful of Thioridazine intense
solution (100 mg/cc) is diluted with water up to 1
quart, what is the % of drug in the final solution?
a.
b.
c.
d.
1.25%
0.005%
0.156%
2.75%
16.
If 10 teaspoonfuls of Risperdal oral solution (100 mcg/5 cc) are diluted with water up to
480 cc, what is the concentration of drug in mcg/
cc in the final solution?
a.
b.
1.2 mcg/ml
2.5 mg/ml
www.pharmacyexam.com
Krisman
c.
d.
2.083 mcg/ml
5.10 mcg/ml
17.
How many cc of 10% Benzoyl peroxide
are required to prepare a 5% 20 cc Benzoyl
peroxide solution?
a.
b.
c.
d.
10 cc
50 cc
25 cc
100 cc
18.
How many milligrams of Clindamycin are
present in 60 cc of 0.1% topical gel of
clindamycin?
a.
b.
c.
d.
100 mg
30 mg
60 mg
45 mg
19.
How many tablets of 250 mg erythromycin are required to prepare 500 cc of 2% topical
solution of erythromycin?
a.
b.
c.
d.
10
40
80
20
20.
If 325 mg of ferrous sulfate contains 22%
elementary iron, how many milligrams of
elementral iron will the patient receive with each
dose?
a.
b.
c.
d.
20 mg
60 mg
71.5 mg
50 mg
21.
If niferex liquid solution provides 10 mg
of elementral iron in 1 teaspoonful, how many cc
of solution are required to provide 55 mg of
elementral iron ?
88
Reference Guide For Pharmaceutical Calculations
a.
b.
c.
d.
27.5 cc
12.5 cc
25.0 cc
30.5 cc
22.
If 30 gm of 0.1% Triamcinolone cream
are mixed with 70 gm of 0.25% Triamcinolone
cream, what is the % w/w of Triamcinolone in the
final mixture?
a.
b.
c.
d.
0.15%
0.005%
0.205%
0.27%
23.
If a prescription reads “50 mg Haldol
decanoate I.M. every week”, how many vials of
Haldol decanoate (10 mg/cc, 5 cc) are required
to dispense a 30 day supply of the drug?
a.
b.
c.
d.
4 vials
1 vial
2 vials
10 vials
Krisman
26.
If the ratio of ionized to unionized is 105
and pKa = 3, what is the pH of the solution?
a.
b.
c.
d.
2
7
8
4
27.
If a prescription calls for “Amoxicillin 500
mg by mouth twice a day for 10 days”, how many
cc of Amoxicillin 125 mg/5 cc are required to
dispense a 10 day supply?
a.
b.
c.
d.
400 cc
200 cc
100 cc
50 cc
28.
What is the weight in grams of 50 cc of
glycerine having a specific gravity of 1.25 gm/cc?
a.
b.
c.
d.
40 gm
62.5 gm
0.025 gm
6.25 gm
24.
If 1000 tablets of Zyvox cost $8550, and
the mark up on the prescription is 15%, what
would be the retail price of 30 tablets?
29.
What is the volume of 10 lbs of chloroform having a density of 1.5 gm/ml?
a.
b.
c.
d.
a.
b.
c.
d.
$294.97
$125.10
$312.5
$111.12
3026 cc
1232 cc
456 cc
585 cc
25.
How much betamethasone is required to
prepare 80 gm of 0.05% ointment ?
30.
How many milliosmols/L are representated by 1000 cc 0.9% sodium chloride?
a.
b.
c.
d.
a.
b.
c.
d.
25 mg
145 mg
40 mg
75 mg
307.7
111.2
235
55
31.
How many milliosmols per liter are
representated by a 50 cc 50% sodium bicarbonate solution? [mw = 84 gm/mole]
www.pharmacyexam.com
89
Reference Guide For Pharmaceutical Calculations
a.
b.
c.
d.
2345
11904
1232
556
32.
How many milliosmols per 100 cc are
representated by a 100 cc 0.1% sodium phosphate solution? [mw of Na3(PO4)= 259]
a.
b.
c.
d.
19.3
23.4
5.06
1.54
Krisman
a.
b.
c.
d.
3.04
1.21
2.50
6.87
37.
How many 325 mg tablets of aspirin are
required to prepare 30 tablets of 10 grains?
a.
b.
c.
d.
45
90
60
75
33.
Calculate the ratio of ionized to unionized drugs at a pH = 5. [ pKa = 3]
38.
Calculate the dose for a 3-year old child.
An adult dose of the drug is 500 mg. [use young
rule]
a.
b.
c.
d.
a.
b.
c.
d.
1:100
100:1
10:1
1:10
34.
What is the PH of a solution having a ratio
of ionized drugs to unionized drugs of 100:1?
[PKa = 5]
a.
b.
c.
d.
3
5
7
2
35.
How many 150 mg Clindamycin capsules
are required to prepare 480 cc of 1% topical
solution?
a.
b.
c.
d.
23
14
56
32
36.
If 5 tablets each of weighing 500 mg of
erythromycin are added to 240 cc of 2% erythromycin topical solution, what is the % of erythromycin in the final solution?
www.pharmacyexam.com
100 mg
50 mg
650 mg
180 mg
39.
If an adult dose of drug is 750 mg, what
is the dose for a child weighing 25 lbs?
a.
b.
c.
d.
250 mg
81 mg
125 mg
375 mg
40.
If an adult dose of drug is 500 mg, what
is the dose for a person having a body surface
area of 130 mm2?
a.
b.
c.
d.
121.11
375.72
456.98
234.65
41.
If the recommended dose of levofloxacin
is 7.5 mg/kg/day, how many 125 mg/50 cc ready
to infuse bags are required to fill the order ?
[patient’s weight = 170 lbs]
90
Reference Guide For Pharmaceutical Calculations
a.
b.
c.
d.
8.00 bags
4.63 bags
2.50 bags
3.25 bags
42.
If the prescription calls for “125 mcg by
mouth four times a day for 30 days”, how many
1/250 grain tablets are required to fill a 30 day
supply?
a.
b.
c.
d.
25
58
75
34
43.
If a prescription calls for “Lanoxin 0.375
mg by mouth every day”, how many cc of Lanoxin
pediatric elixir (50 mcg/cc) are required to
dispense a 30-day supply?
a.
b.
c.
d.
150 cc
225 cc
350 cc
450 cc
44.
If 2 gms of dextromethorphan are dissolved in 1000 cc of water, how many grains of
dextromethorphan are present in 1 tablespoonful
of solution?
a.
b.
c.
d.
1.2 gr
0.85 gr
0.46 gr
0.95 gr
45.
What is the dose of a rocephine for a
patient that has 140 mm2 body surface area?
The average adult dose of drug is 500 mg.
a.
b.
c.
d.
123.12 mg
226.18 mg
404.62 mg
560 mg
www.pharmacyexam.com
Krisman
46.
How many grams of sodium chloride are
required to prepare 1000 cc of 0.45% normal
saline solution?
a.
b.
c.
d.
9.0 gm
2.2 gm
4.5 gm
1.2 gm
47.
How many calories are provided by 500
cc of D5W solution?
a.
b.
c.
d.
34 kcal
25 kcal
44 kcal
85 kcal
48.
How many grams of dextrose are required
to prepare 10 L of 1 in 500 dextrose solution?
a.
b.
c.
d.
12 gm
10 gm
45 gm
20 gm
49.
What is the % of acetic acid in 1 in 50
solution?
a.
b.
c.
d.
2%
0.5%
1%
5%
50.
To dispense 7% of 240 cc solution of
risperdal, how many cc of stock solution are
required? [stock solution: 100 mg/cc, 1000]
a.
b.
c.
d.
168 cc
222 cc
123 cc
145 cc
51.
If a half pint of risperdal oral solution (1
mg/cc) is diluted with water up to 1000 cc, what
is the strength of drug in mg/cc in the final solution?
91
Reference Guide For Pharmaceutical Calculations
W.H.O. recommends 0.45 grams of protein per
kilogram of ideal body weight per day. How many
bottles of Ensure Plus are required daily for a
person weighing 120 lbs?
a.
b.
c.
d.
2
5
7
9
359. Each 8-ounce Ensure Plus labeling provides
the following information:
Amount/serving
Total fat (11gm)
Saturated fat (1gm)
Trans fat (0gm)
Cholesterol (< 5mg)
Sodium (240mg)
Potassium (500mg)
Protein (13gm)
Carbohydrate (50gm)
Sugar (18gm)
Krisman
Multiplication
Factor
Oxycodone
0.25
Codeine
0.04
Morphine
0.12
Meperidine
0.02
Hydromorphone
1.0
Oral Prior
Opioid
a.
b.
c.
d.
10
6
3
25
%DV Serving Size
17%
5%
(8 fl oz)
(350 calories)
361. A prescription says to take 15mg of
Morphine po q4h. Below is a chart with the
recommended initial Duragesic dose based upon
daily oral Morphine dose:
< 2%
10%
14%
26%
17%
Morphine Dose
(daily in mg)
45-134
135-224
225-314
315-404
If we mix 250mg of KCl powder with 4 ounces
of Ensure Plus, what would be mEqs of KCl in a
final mixture? (K = 39, Cl = 35.5)
a.
b.
c.
d.
Parenteral
Prior
Opioid
N/A
N/A
N/A
N/A
N/A
5.96
6.71
3.46
1.52
360. A 42-year-old patient is taking 10mg of
Meperidine by mouth four times a day to relieve
pain associated with a knee injury. If a prescriber
want to switch him over to Hydromorphone, how
many mls of 0.8mg/ml Hydromorphone suspension are required to fill a 72-hour supply?
www.pharmacyexam.com
Duragesic Dose
(mcg)
25
50
75
100
How many 25mcg/hr Duragesic patches are
required to fill a 10-day supply?
a.
b.
c.
d.
3
9
12
10
362. A 65-year-old patient is taking 5mg of
Meperidine by mouth, six times day, to relieve
pain associated with lung transplantation. If a prescriber wants to swit ch him o ver to
Hydromorphone, how many mls of 0.6mg/ml
Hydromorphone suspension are required to fill a
7-day supply?
127
Reference Guide For Pharmaceutical Calculations
Oral Prior
Opioid
Multiplication
Factor
Oxycodone
Codeine
Morphine
Meperidine
Hydromorphone
a.
b.
c.
d.
Parenteral Prior
Opioid
0.25
0.04
0.12
0.02
1.0
N/A
N/A
N/A
N/A
N/A
28
21
14
7
a.
b.
c.
d.
5
10
15
20
365. A 55-year-old patient is taking 15mg of
Meperidine by mouth, four times day, to relieve
pain associated with brain tumor. If a prescriber
wants to switch him over to Hydromorphone, how
many mls of 2mg/ml Hydromorphone suspension
are required to fill a 10-day supply?
Oral Prior
Opioid
363. A prescription says a 50mcg/hr patch of
Duragesic TDS is to be changed every 72 hours.
If a prescriber wants to switch this to Oxycodone,
how many 5mg tablets of Oxycodone are required
to fill a 7-day supply? (Assume 18 hrs after removal of the transdermal fentanyl patch,
approximately 5mg of oxycodone q12h can be
substituted for each 25mcg/h of transdermal
fentanyl to start.)
a.
b.
c.
d.
Krisman
140
120
52
28
Oxycodone
Codeine
Morphine
Meperidine
Hydromorphone
a.
b.
c.
d.
Multiplication
Factor
0.25
0.04
0.12
0.02
1.0
Parenteral Prior
Opioid
N/A
N/A
N/A
N/A
N/A
6
9
12
18
364. A prescription says to take 30mg of
Morphine po q6h. Below is a chart with the
recommended initial Duragesic dose based upon
daily oral Morphine dose:
Morphine Dose
(daily in mg)
Duragesic Dose
(mcg)
45-134
135-224
225-314
315-404
25
50
75
100
How many 25mcg/hr Duragesic patches are
required to fill a 30-day supply?
www.pharmacyexam.com
128
Reference Guide For Pharmaceutical Calculations
Krisman
ANSWERS FOR PRACTICE TEST
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
B
C
B
A
C
D
C
D
C
D
A
C
A
C
C
C
A
C
B
C
A
C
A
A
C
C
A
B
A
A
B
D
B
C
D
A
C
A
C
B
B
B
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
www.pharmacyexam.com
B
C
C
C
D
D
A
A
C
C
D
A
D
A
D
D
C
B
A
A
B
B
A
B
C
C
D
A
A
B
B
B
B
D
C
A
B
C
D
A
A
A
85.
86.
87.
88.
89.
90.
91.
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
110.
111.
112.
113.
114.
115.
116.
117.
118.
119.
120.
121.
122.
123.
124.
125.
126.
B
B
C
C
D
A
B
C
A
B
C
D
A
A
B
C
A
B
A
A
A
C
D
A
A
C
C
D
B
A
B
B
C
C
D
D
D
D
A
B
C
C
127.
128.
129.
130.
131.
132.
133.
134.
135.
136.
137.
138.
139.
140.
141.
142.
143.
144.
145.
146.
147.
148.
149.
150.
151.
152.
153.
154.
155.
156.
157.
158.
159.
160.
161.
162.
163.
164.
165.
166.
167.
168.
D
A
A
B
C
D
C
B
C
A
A
A
B
D
D
B
B
B
C
D
A
B
A
B
C
C
C
C
D
C
C
C
D
C
C
C
B
A
A
A
A
A
129
Reference Guide For Pharmaceutical Calculations
345.
346.
347.
348.
349.
350.
351.
352.
353.
354.
355.
356.
357.
358.
359.
360
361.
362.
363.
364.
365.
Krisman
C
D
D
C
D
A
C
A
A
A
B
C
A
A
B
C
A
D
D
B
A
www.pharmacyexam.com
131